Two-Layer Erbium-Doped Air-Core Circular Photonic Crystal Fiber Amplifier for Orbital Angular Momentum Mode Division Multiplexing System

Hu Zhang,Wenbo Zhang,Zhuo Zhang,Xiaoguang Zhang,Di Han,Hui Li,Lixia Xi

doi:10.3390/cryst9030156

Abstract

Orbital angular momentum (OAM) mode-division multiplexing (MDM) has recently been under intense investigations as a new way to increase the capacity of fiber communication. In this paper, a two-layer Erbium-doped fiber amplifier (EDFA) for an OAM multiplexing system is proposed. The amplifier is based on the circular photonic crystal fiber (C-PCF), which can maintain a stable transmission for 14 OAM modes by a large index difference between the fiber core and the cladding. Further, the two-layer doped region can balance the amplification performance of different modes. The relationship between the performance and the parameters of the amplifier is analyzed numerically to optimize the amplifier design. The optimized amplifier can amplify 18 modes (14 OAM modes) simultaneously over the C-band with a differential mode gain (DMG) lower than 0.1 dB while keeping the modal gain over 23 dB and noise figure below 4 dB. Finally, the fabrication tolerance and feasibility are discussed. The result shows a relatively large fabrication tolerance in the OAM EDFA parameters.

Highlights

Optical communication technology has developed rapidly in the past decades
mode-division multiplexing (MDM) utilizing the orthogonality among different orbital angular momentum (OAM) states as the multiplex method has exhibited promising prospects in recent years
L can be any integer value, which means that OAM has great potential to increase the transmission

Summary

Introduction

Optical communication technology has developed rapidly in the past decades. All kinds of multiplexing and high order modulation technological have greatly increased the capacity of single fibers. A liquid-crystal spatial light modulator is another promising scheme for generating OAM modes, which exhibits some good properties including simplicity, high efficiency, and reconfiguration [8,9,10] Another is the optical vortex beam transmission, which needs the fiber supporting OAM modes. Most designs of OAM-EDFA are based on the ordinary circular air-core fiber with a one-layer doped region [23,24,25,26]. These OAM-EDFAs perform well in the modal gains but the DMG still needs to be improved. All 14 OAM modes are amplified as as possible to achieve long-haul transmission

Theory

Analysis andan

Conclusions